At present, the main/standby backup of single boards is basically adopted in communication equipments having high requirements on reliability, in order to ensure that, in case a fault occurs in the current main single board, another standby single board is able to timely replace the main single board in fault to keep the normal running of the whole system.
The main/standby switching of the single boards is performed generally due to the following three reasons:                1. a switch instructed by operator (a switching by background human-computer commands);        2. fatal faults in a main single board (such as, removal, power failure, heartbeat signal loss and reset of the main single board, etc); and        3. nonfatal faults in a main single board.        
The principle for switching the main single board with the nonfatal fault is that: the fault states of the main and standby single boards are graded at first; and the current fault levels of the single boards are given by the self-diagnosis function of the single board software and notified to the opposite board in real time. A system compares the fault levels of the two single boards, and allows a switch between the main single board and the standby single board when the fault level of the main single board is higher than that of the standby single board; otherwise, the current main/standby state remains unchanged. However, along with diverse communication system services and detailed system functional levels, many boards with a plurality of Micro Controller Units (MCUs) has appeared inevitably, particularly network element control single boards in which main/standby backup is generally indispensable. In the related technologies, the application of the single board with a plurality of MCUs has a higher requirement on the main/standby switching mechanism for the conventional single board with a single MCU, specifically as follows:                firstly, each MCU in the single board with a plurality of MCUs is generally able to work separately, that is to say, it can still work normally without other MCUs, which will bring trouble to the deployment of a main/standby switching control software module, i.e., whether the running program of each MCU should comprise the main/standby switching control software module;        secondly, the running program on each MCU has its own fault monitoring mechanism; and the determination of the final fault grade for switching will be very complex when the programs on a plurality of MCUs detect faults at the same time.        
It can be seen from the two above-mentioned standpoints that, the main/standby switching of the single board with a plurality of MCUs will become complex if the main/standby switching mechanism for the single board with one MCU is adopted.